FIG. 1 is a block diagram depicting a conventional facsimile signal transmitting device. In FIG. 1, reference numeral 1 denotes a facsimile terminal; 2 denotes a modem which demodulates facsimile signals provided from the facsimile terminal 1 and modulates base band facsimile signals transmitted from another facsimile terminal 8; 2a denotes a demodulator of the modem 2; 2b a modulator of the modem 2; 3 denotes a T. 30 communication protocol control part; 4 denotes a modem control part which controls the modem 2 in accordance with a mode setting information provided from the T. 30 communication protocol control part 3 which controls the communication protocol of facsimile signals; 5 denotes a frame assembling part whereby, based on a signal provided from the T. 30 communication protocol control part 3 and indicating the kind-of each facsimile signal, base band facsimile signals demodulated by the modem 2 are sequentially combined into frame data of a predetermined size and from which the frame data is provided onto a transmission line 6; 6 denotes the transmission line; and 7 denotes a frame disassembling part which, when the frame data of a predetermined size is provided onto a transmission line 13, receives and disassembles the frame data into a plurality of base band facsimile signals and applies them to the modem 2.
Reference numeral 8 denotes a facsimile terminal; 9 denotes a modem of the same function as that of the modem 2; 9a denotes a demodulator of the modem 9; 9b denotes a modulator of the modem 9; 10 denotes T. 30 communication protocol control part of the same function as that of the T. 30 communication protocol control part 3; 11 denotes a modem control part of the same function as that of the modem control part 4; 12 a frame assembling part of the same function as that of the frame assembling part 5; 13 denotes the transmission line; and 14 denotes a frame disassembling part of the same function as that of the frame disassembling part 7.
Next, the operation of the conventional facsimile signal transmitting device will be described.
A description will be given, for convenience's sake, of an operation for transmitting facsimile signals from the facsimile terminal 1 to 8.
In the case of transmitting facsimile signals from the facsimile terminal 1 to 8, the facsimile signals provided in modulated form from the facsimile terminal 1 are demodulated by the demodulator 2 of the modem 2 for conversion into base band facsimile signals so as to improve the facsimile signal transmission efficiency.
And, when the base band facsimile signals are output from the demodulator 2a of the modem 2, the frame assembling part 5 sequentially combines the base band signals into frame data of a predetermined size on the basis of a signal from the T. 30 communication protocol control part 3 that indicates the kind of the facsimile signal concerned.
Upon completion of the generation of the frame data of a predetermined size, the frame assembling part outputs the frame data onto the transmission line 6, with which the transmission of the facsimile signals finishes.
When the frame data is provided onto the transmission line 6 as described above, the frame disassembling part 14 responds to a frame detection signal (a signal indicating the data structure of the frame data concerned and the presence or absence of data discarded during transmission) to disassemble the frame data into a plurality of base band facsimile signals, outputting them to the modem 9.
The frame detection signal mentioned herein is a signal that is provided from a frame discard detecting part (not shown) which makes a check to see if frame data from the frame assembling part 5 has been discarded during transmission over the transmission line 6.
When the plurality of base band facsimile signals are output from the frame disassembling part 14, the modulator 9b of the modem 9 sequentially modulates and provides them to the facsimile terminal 8, with which the reception of the facsimile signal finishes.
The facsimile terminal 8 demodulates the modulated facsimile signals received from the modulator 9b of the modem 9 and performs printing or some other process in accordance with the result of demodulation.
No description will be given of the operation for transmitting facsimile signals from the facsimile terminal 8 to 1 because it is the same as in the case of facsimile signal transmission from the facsimile terminal 1 to that 8.
Because of such a configuration as described above, the conventional facsimile signal transmitting device provides for enhanced efficiency in the transmission of facsimile signals. However, when frame data is discarded by reason of congestion of the transmission line 6 or for some other reason, the fact that the frame data has been discarded can be recognized based on the frame detection signal. However the discarded frame data cannot be sent to the facsimile terminal 1 of the receiving side. Therefore when control data necessary for facsimile communication is contained in the discarded frame data, the possibility exists that the facsimile terminal 1 or the like will terminate through a communication failure. When image data is contained in the discarded frame data, the fax image will suffer serious degradation.
The present invention is intended to solve such problems as mentioned above, and has for its object to provide a facsimile signal transmitting device and a facsimile signal transmitting method which prevent the occurrence of a communication disorder at a facsimile terminal and avoids a serious deterioration of fax images.